The United States Bureau of the Census gathers a variety of useful
information when it conducts the census. This information covers an
array of topics pertaining to the lifestyles, incomes, jobs, and
families of United States citizens. Small "samples" are extracted from
the data and are collectively called the Public Use Microdata Samples
(PUMS).

The PUMS are computer-accessible files that contain records for a
sample of housing units, with information on the characteristics of the
units and the people in them. Within the limits of the sample size and
geographic detail, you can use the PUMS to complete several types of
tabulations.

The 1990 PUMS contain individual- and household-level information from
the long form questionnaires distributed to a sample of the population
enumerated in the census.

The PUMS are available in samples that represent:

5% of the Population and Housing of the U.S.

which identifies all States and various subdivisions within them,
including most counties with 100,000 or more inhabitants.

1% of the Population and Housing of the U.S.

which identifies all metropolitan territory and most M.A.s with
100,000 or more inhabitants individually, and groups of M.A.s elsewhere.

Selected group quarters are also included. The file contains
individual weights for each person and housing unit. When applied to
the individual records, the weights expand the sample to the total
population. Both the 5% and 1% samples have the same subject content
and vary only in geographic composition of the Public Use Microdata
Area (PUMA). Each dataset is a subsample of the full census sample
(approximately 15.9% of all household units) that received census
long-form questionnaires.

The 1990 data collection were prepared by the United States Bureau of
the Census. All data released by the U.S. Bureau of the Census are
subject to strict confidentiality measures imposed by U.S. legislation
(Title 13, U.S. Codes). The census data can be used for statistical
purposes only. The PUMS records contain information on the
characteristics of housing units and the people in them. The PUMS are
extracted from the census data in a manner that avoids disclosure of
information that can identify households or individuals. To protect
the confidentiality of the respondents, any information that would
identify a household or an individual is excluded.

Microdata records identify no geographic area with fewer than 100,000
inhabitants. Microdata samples include only a small fraction of the
population, drastically limiting the chance that the record of a given
individual is even contained in a PUMS file, much less identifiable.

For more information on 1% vs 5% sample files consult the PUMS
home-page.

Resolution:
Geographic identification of the location of the sampled households
includes Census regions and divisions (e.g., Standard Metropolitan
Areas (SMAs) and State Economic Areas (SEAs)), and each state).

The datafile is documented in a codebook containing a data dictionary and
supporting appendix information. Information on data processing, accuracy of
the data, and sample design is also included.

Layout:

The PUMS from the 1990 Census contain individual- and household-level
information from the "long-form" questionnaires distributed to a sample
of the population enumerated in the Census. Each of the discrete PUMS
files contains two types of records: "household" records and "person"
records. Although the length of each of these record types is identical
(231 charaters), the files are hierarchical in structure; each person
record has a logical and physical relationship to the household record
which precedes it.

Each household record is followed by a varying number of person records
(one for each member of the household). Data items in this collection
include the individual responses to the basic social, demographic, and
economic questions asked of the population in the 1990 Census
of Population and Housing.

Universe:

Information from the census was derived either from questions
asked of the entire population or from questions asked of only a sample
of the population. Those questions asked about every person and housing
unit are called 100-percent or short-form questions. The others are
called sample or long-form questions.

Those households receiving the short-form questionnaires were asked
only the 100-percent questions, and those receiving the long form were
asked both the 100-percent questions and the sample questions.
Sampling rates vary depending on geographic location and population
size.

PUMS data contain a sample of the individual long-form census records
showing most population and housing characteristics with identifying
information removed.

The coding system varies for each census, so it is important to have
access to the codebook for each census in order to assess the meaning
of a specific field in a census record and its comparability across
censuses. Very little comparability exists between geographic
identifiers on each of the previous files, but housing and population
characteristics are similar.

The sample questionnaires were edited for completeness and consistency,
and substitutions or allocations for any missing data were made.
Allocation flags appear at the end of each record to indicate when an
item has been allocated. A user wishing to tabulate only actually
observed values can eliminate variables with allocated values.

Variables:

The datafile(s) contain two record types:

Household:

which contain variables describing the location and composition of
the household. It also contains records of group quarters members.

Person in the household:

which contain demographic variables such as nativity, marital
status, family membership, number of children, veteran status, wage
deductions for social security, education, employment status, income,
and occupation.

Summary Tape Files
(STF) are designed to provide statistics with greater subject detail
for geographic areas than is feasible or desirable to provide in
printed reports. The census data contained in printed reports are
arranged in tables. Population and housing characteristics are
presented for specified geographic areas; for example a table may
represent the number of rented housing units in a census tract, the
number of persons 65 years of age or older in a city, or the total
population of a county. Census data at the small-area level, such as
census tracts and smaller, will contain limited subject matter detail.
STF files, in machine readable format, mimic this table layout.

RELATED PUBLICATIONS:

For more information on the 1990 PUMS dataset, refer to the 1990
Census of Population and Housing Public Use Microdata Sample Technical
Documentation. For a copy of the documentation, contact Data User
Services Division, Systems and Programming Branch, Bureau of the
Census, Washington, D.C. 20233. Telephone: (301) 763-4100.